Push-to-talk (PTT) and/or Push-to-X (PTX) communication systems, may be implemented over various radio communications networks such as, but not limited to, CDMA, 3GGP™ and WLAN. Common to most such networks is the necessity of performing Location Area Updates (LAU) or Routing Area Updates (RAU) as a mobile station moves through various network radio coverage and/or controller or switch control areas. A Routing Area may be defined by a switching area or control area such as a base station controller area, and will comprise one or more base station coverage areas which are sometimes referred to as “cells.”
Delays issues occurring due to RAUs or location updates may be problematic when communicating using PTT and/or PTX systems. For example, PTT over General Packet Radio Service (GPRS) may require lengthy RAU procedures causing a resulting poor performance as perceived by a mobile station user.
A GPRS RAU will occur on a mobile station's change of cell when the Routing Area changes. A GPRS core network comprises various network entity components one of which is the Serving GPRS Support Node (SGSN). The SGSN, similar to a base station, base station controller, or switch, defines a routing area within which data packets are routed by the SGSN to the appropriate mobile station when it is within the SGSN area of coverage or control. The SGSN therefore creates another location updating requirement for a mobile station moving through a GPRS network.
For example, Routing Area Update may occur Intra-SGSN or Inter-SGSN as the mobile station moves between various SGSN control areas. The delay that could occur due to such RAU procedures is approximately 2 to 4 seconds for an Intra-SGSN RAU, but may be between 8 to 30 seconds for an Inter-SGSN RAU. Intra-SGSN RAUs are therefore typically short enough such that buffering in the PTT system can significantly help hide the data outage due to the RAU from a mobile station user. Thus the overall outage duration from intra-SGSN RAUs is generally short enough to be tolerable to end users.
However, the data outages due to inter-SGSN RAUs cannot be hidden from end users and thus often generate significant end user confusion. The PTT or PTX floor is generally locked by one mobile station during the duration of the RAU. Thus for example, the user having the floor may be talking or otherwise transmitting for many seconds without realizing that the intended recipient user or users cannot hear anything or otherwise cannot receive the transmitted data.
The listening user may experience having their mobile station locked into the listening state and further being silent and non-responsive to key strokes for up to 30 seconds or more. Therefore it is understandable that an inter-SGSN RAU may significantly disrupt the flow of conversation and generally annoy both end users.
Further, if a transmitting mobile station user or talker engaged in a group call experiences an inter-SGSN RAU, all users in the call will be significantly disrupted. If any one of the listeners experiences the RAU, that listener will not only lose a large part of the conversation but will also lose a significant part of his opportunity to gain the floor.
Other network technologies may manifest similar difficulties for PTT. For systems defined by the 3rd Generation Partnership Project 2 (3GPP2) such as CDMA2000 systems, there is the CDMA concept of a soft handoff where a mobile station may switch to another base station's coverage. The soft handoff approach of course relies upon the target base station having a channel with the desired Pseudo Random Number (PRN)/frequency being available for the handoff. If the PRN is not available, or in cases where the handoff is between base stations of different carrier networks, then a hard handoff will likely result which may result in a PTT data outage.
For 3GPP, the problem may manifest itself in inter-domain handoffs, such as between subnets when a user moves between subnets and mobile IP is enforce. In an inter-domain handoff versus an intra-domain handoff, there is usually a longer message path and more messaging causing a potential PTT data outage.
Generally hard handoffs between technologies such as, but not limited to 3GPP to GSM or WLAN to GSM and others may require hard handoffs that are disruptive and add delay to the transmission and reception of PTT and/or PTX data.
Therefore what is needed are apparatuses and methods for dealing with PTT and/or PTX data outages to improve user perception and experience when such anticipated data outages occur during PTT and/or PTX communication sessions.